In a side airbag device for protecting an occupant from the impact of a side collision by deploying an airbag 11 in a fore-and-aft direction of the vehicle body from a door inner face between the inner face and the occupant, an arrangement in which the airbag 11 is formed by stitching outer peripheral parts of a window side reinforcing fabric 14, an occupant side first cut fabric 15, and a second cut fabric 16 sandwiched therebetween, an airbag main body 12 is formed by the first cut fabric 15 and the second cut fabric 16, a space 19 is formed between the reinforcing fabric 14 and the second cut fabric 16, and the interior of the airbag main body 12 and the space 19 communicate via a vent hole 20 formed in a central part of the second cut fabric 16 is known from Patent Document 1 below.
In accordance with this side airbag device, when the airbag main body 12 is deployed by gas generated by an inflator 17, part of the gas passes through the vent hole 20 formed in the central part of the second cut fabric 16 and makes the space 19 expand, and it is thus possible to protect the airbag main body 12 even if broken window glass pieces scattered by the impact of a side collision damage the reinforcing fabric 14.    Patent Document 1: Japanese Patent Application Laid-open No. 10-76903